The invention relates generally to traction motor control systems, and relates more particularly to locomotive traction motor suspension and current control systems.
Traction motors for locomotives are typically coupled to drive gears for each respective axle of the locomotive. The amount of current to the traction motors is controlled so that proper propulsion may be carried out depending upon loading conditions of the engine. Axle mounted traction motors are typically connected to and suspended from their respective axle such that a plain end is connected to a portion of the truck and another portion of the traction motor is coupled about the moving axle through a "U-Tube" as known in the art. A problem arises with locomotive traction motors when the traction motor suspension bearings overheat.
In general, typical traction motor suspension bearing configurations include an inner angled roller bearing secured between an inner cone which is proximate the axle and an outer cup. The cup and cone allow rotation of the roller bearing. A suspension bearing housing encloses the cup, roller bearing and cone configuration and protects the bearing assembly from external elements. The suspension bearing housing is typically a "U-Tube" and extends circumferentially one half the way around the axle. The traction motor is supported on its one end by the "U-Tube" and bearing connection, and is supported to a fixed support on the truck at its other end.
The traction motor suspension bearings may overheat for a variety of reasons including lack of bearing lubricant, a cracked bearing housing, or other fault caused by various stress loading. The overheating of the traction motor suspension bearings may cause a locked axle or cause the traction motor to be separated from its mounting structure. This may result in the cutting or locking of the axle causing a derailment. Consequently, there exists a need for a hot bearing detection system for locomotive traction motors.
Generally, hot bearing detection is known for axle bearings on locomotives. Such hot axle bearing detection may be facilitated by a wayside heat detection unit that detects the overheating of an axle bearing as the locomotive travels down the tracks. For example, a wayside infrared energy detecting sensor detects hot axle bearing as the train travels along the tracks. The infrared detection sensor may be placed on the outside of a track and be coupled to a railroad tie so that the sensor points vertically to detect the overhanging or outboard axle bearing. Such wayside sensing units are used along railways to detect the overheating of axle bearing to avoid derailments or other serious malfunctions caused by axle bearing overheating.
When axle bearings are located between wheels of a locomotive, e.g., inboard axle bearings, a hot bearing sensor is typically placed proximate to the inboard axle bearing to detect the temperature of the axle bearing to avoid overheating as previously discussed. A communication link among coupled rolling stock is toggled to indicate that a hot axle has been detected. However, such mechanisms are not generally known for traction motor bearings.
Another problem with traditional tractor motor control systems, is that they typically fail to adequately protect brake life and traction motor life. Traction motors receive their drive current from an alternator which is typically driven by a diesel engine. A computer typically controls the amount of drive current to the traction motors. Locomotive operators often attempt to maintain a tight linkage between rolling stock such as cars in the train while stopping or traveling along tracks to minimize jerking. For example, when locomotives and cars are traveling over mountainous terrain, the operator attempts to manually control the locomotive so as to maintain a tight linkage among the cars. Such manual control is accomplished by applying the power brake when the locomotive is in motoring. Such control is termed stretch braking. Motoring is a term to indicate that the locomotive is being asked to apply alternator power to the traction motors. However, a problem arises during stretch breaking when the operator applies power braking for an extended period. As a consequence, the traction motors may experience excessive overheating, and the power brakes will experience excessive wear.